The present invention relates to tooling for use in connection with, for example, injection molding, and more specifically to retaining mechanisms employed to restrain and lock tooling core pieces in their retracted position when the mold is open.
Injection mold tools are generally defined by a pair of mold members or die halves which part to expose and effect release of the molded piece part contained within the mold. For non-complicated parts, the mold tool members are simply separated with the molded component being pushed outwardly from the mold member in which it rests. For a large percentage of molds, however, piece geometry requires use of tool core members which must be withdrawn laterally, i.e. parallel to the parting plane separating the mold halves, from the molded part before that part can be released from the mold. These core members are designed to automatically cycle between retracted and inserted positions as the mold halves are correspondingly reciprocated between respective parted (i.e. part release) and mated (i.e. part mold) positions.
More specifically, the core members are affixed to movable portions of the tool commonly known as slides. As noted, a slide must be advanced to properly position the core member within the mold for part fabrication and thereafter retracted to facilitate part release. The present invention relates to mechanisms, known as retainers, employed to hold the slide in its retracted position while the mold is open.
Not all slides require retainers. Gravity, for example, may serve the retainer function for slides positioned below the tool die. However, many tools require multiple core members thereby necessitating placement of slides laterally or above the mold die. It is critical that these slides remain securely positioned in their retracted positions until the next recycled closure of the mold. Should the slide be misplaced during die closure, substantial damage or destruction of the mold may occur. Machined tool molds represent expensive investments, not uncommonly exceeding tens or hundreds of thousands of dollars.
Slide retainers are not new. Several well-known designs are commercially available. As set forth in more detail herein, the present slide retainer offers several important advantages over these known designs including the very important feature of guaranteed slide retention.
A principal limitation of currently available slide retainers is the absence of a positive lock against inadvertent slide release. Each of the prior art structures employs spring-loaded jaws or cams or, in one known device, simply the clasping pressure afforded by elastically deforming plastic material to grip and retain the core slide. But each of these retention schemes has, in the first instance, a relatively low finite slide-holding potential or limit and, furthermore, the not-insignificant possibility of complete retention failure due to fatigue occasioned by the long-term cycling of the linear compression springs therein or, in the case of the elastically deformed plastic retainer, simple wearing of the plastic.
But it is the relatively low and finite overall load limit of these devices that represents one of their most significant shortcomings. These retainers, even if properly maintained and replaced according to manufacturers recommendations, can still cause the disastrous release of the core slide members due, as above noted, to the finite load limits thereof. The present retainer, by contrast, offers among other advantages a positive locking feature that virtually guarantees against unscheduled slide movement.
One well-known slide retainer is described in U.S. Pat. No. 3,811,645 to Feist. This retainer is typically mounted on the movable base member of the tooling die and defines a pair of spring-loaded jaws into which a pin, extending from the slide member, is received as the slide is urged, for example upwardly, to its fully core-retracted position. The jaws clamp the pin thereby, at least in theory, precluding its release and downward return into the die. There is nothing to foreclose the release of the slide other than the limited grasping ability of the spring-loaded jaws themselves. Indeed, upon tool closure the slide retention pin is forced--against this spring pressure--out of engagement within the locking jaws.
While such spring-loaded locking jaws are designed to hold specified slide weights, unexpected roughness (i.e. bumping or jerking) of the molding press or, even more likely, the inadvertent bumping of the slide by persons servicing the press, has been known to result in slide release. By contrast, the slide retainer described herein positively receives and positions the slide pin within a machined channel and behind a solid island of material thereby locking the slide against inadvertent release in the face of any conceivable load placed thereon. And, as previously noted, linear compression springs of the type shown by Feist are known to fatigue and fail if subjected to prolonged use and therefore must be periodically replaced to minimize the likelihood of retainer failure.
A further disadvantage of the Feist-type retainer overcome by the present invention is that related to the mounting thereof. Feist retainers are customarily affixed to the movable mold base above--in the case of a vertically retracting slide--the maximum upward travel thereof. As these retainers require between 11/2 to 31/2 inches of "real estate" for proper attachment, the mold base upon which the retainer is to be placed must be correspondingly larger. the added size of the required tool base--which is comprised of notoriously expensive machine grade steel--can significantly increase the overall cost of the associated completed tool. A further difficulty with the Feist retainer is its mounting orientation--outwardly of the slide and along the moving axis thereof--necessarily precludes the removal of the slide without, first, either removing the retainer or the slide attachment rails.
By contrast, the present retainer is positioned within the base and below the path of slide travel. In this manner, neither increased base volume is required to mount the retainer nor must the retainer be removed prior to removal of the slide.
A similar retainer to that of Feist is the urethane clip described in U.S. Pat. No. 4,998,875. This retainer uses the resiliency or elasticity of the plastic material to effect slide pin capture and locking. But this retainer suffers the same limitations noted above in its mounting and restricted grasping power and in its corresponding absence of any positive slide locking mechanism. Furthermore, while such retainer will not exhibit spring failure, normal wear of the urethane material is viewed as significantly limiting the cycle life of this device.
Yet another known retainer is described in U.S. Pat. No. 4,765,585. This retainer employs a linear spring-loaded plunger or ram--generally mounted to the base--that seats within a mating slotted holder on the slide. This arrangement exhibits many of the above-discussed limitations including limited holding power; the likelihood of linear spring fatigue-induced failure; and the absence of a positive locking mechanism to preclude inadvertent slide release.
As yet a further advantage of the present retainer is its dual-functionality as, foremostly, a positive-locking slide retainer but, secondarily, as a mechanism for properly guiding the associated slide. It is well known that slide guide bars are utilized in most high quality tooling to assure proper and repeatable tracking and positioning of the slide and associated tool core member. As set forth in more detail below, the present retainer may advantageously be configured to effect the secondary, but important, function of slide guiding thereby obviating the expense associated with the addition of conventional slide guide bar arrangements.
The above-noted features of the present slide retainer are achieved through the cooperation of track channel and cylindrical pin inserts mounted, respectively, within the so-called "B" plate of the movable half of the mold and the movable slide. Importantly, both inserts are retained largely within their respective base and slide members, i.e. do not protrude beyond the plane defined therebetween, and therefore do not require removal of either slide component to effect removal of the slide, itself. The track channel, however, may extend into operative engagement with the slide thereby providing the above-described slide guide function. Further, the track insert is positioned within the base generally below or adjacent the ordinary path of slide travel thereby employing portions of the mold base that are ordinarily present and otherwise required for proper tool design and slide operation. In this manner, proper slide retention is achieved without a corresponding increase in the size of the tool base material required.
Actual slide retention is effected through the engagement of a track pin, which pin extends from the cylindrical insert within the slide, across the previously noted plane defined between the slide and base, into a channel defined within the base track insert. Effortless slide removal (i.e. without first removing portions of the retainer or slide rails) is not compromised, however. Ingress/egress channels are provided at the longitudinally opposed ends of the track insert to facilitate this ease of removal.
The track channel defines a "one-way" circumferential course through which the mating track pin navigates during each cycle of the tool. Such uni-directional travel is achieved through the combination of a rotationally biased pin assembly and a uni-directional gate within the channel itself. More specifically, the track pin is rigidly and asymmetrically mounted to the cylindrical insert, the latter member being retained for rotational movement within a corresponding cylindrical slide bore. A torsional spring biases the cylindrical insert for rotation in a predetermined angular direction.
As the slide is retracted following each mold cycle, the track pin enters the circumferential channel being routed in the proper direction through this channel by reason of the previously noted gate. A second torsional spring maintains this gate in a closed position thereby inhibiting pin passage other than in the prescribed direction. It is significant that each of the above-noted springs is of torsional configuration. Such springs, when operated within restricted angular limits as herein, exhibit a substantially unlimited life expectancy thereby eliminating the probability of failure found in retainers employing linear springs.
As the slide reaches its maximum retracted position--a positioned defined by one or more generally conventional angle pins extending from the stationary half of the mold into a mating slide holes--the track pin, under the force of its torsional biasing spring, rotates and, traveling within a substantially lateral region of the track channel, firmly seats within a recess or indentation defined in the channel. This indented, lateral portion of the track channel is heart-shaped--the entire channel dipping at the point of indentation. This dip forms, not only the recess into which the track pin seats, but an opposed channel wall that precludes the continued movement of the track pin through the track channel. Thus, further rotation of the track pin and insert is inhibited until the slide is again engaged by the angle pins upon commencement of the next mold cycle.
A significant feature of the above-described topology is the positive locking achieved thereby. When received within the recessed portion of the track channel, a solid barrier or island of machine steel defined by the track channel wall, absolutely forecloses further movement of the track pin in the release direction, i.e. movement of the slide into the mold. The slide cannot be moved or released regardless of the weight of the slide, the vibration or other roughness of machine operation, or, the inadvertent pressure placed on the slide by persons working on the mold.
Release of the slide occurs only upon commencement of the next mold cycle, more specifically, upon re-entry of the angle pins into the mating holes within the slide. As the beveled end regions of the pins first engage the slide, the slide is forced a small additional distance upwardly thereby lifting the track pin from the track channel recess. Once released from the channel recess, the track pin continues its one-way journey to the end of the lateral portion of the track channel, again, under the rotational force of the spring-biased cylindrical insert.
The track pin is now free to travel downwardly through the remainder of the one-way circumferential channel, under the engagement and urging of the angle pins until it returns to the initial mold position. In completing this movement, the track pin must pass the gate, which uni-directional gate yields to the passage of the track pin in the prescribed return direction.
It is therefore an object of the present invention to provide a slide retainer. The retainer should preferably accommodate a wide range of slide weights and should incorporate positive locking against inadvertent slide release.
A further object of the present invention is a slide retainer that may be affixed to and within the slide and mold base without requiring additional mold base material beyond that otherwise required to implement the desired mold tooling configuration.
Yet another object of the present slide retainer is the elimination of discrete slide guide bars through providing for an integral slide retainer guiding structure.
These and other objects will become apparent from the Drawings and the specification including the Description of the Preferred Embodiment that follow.